ALSA: 6fire: Convert to the common vmalloc memalloc

The recent change (*) in the ALSA memalloc core allows us to drop the
special vmalloc-specific allocation and page handling.  This patch
coverts to the common code.
(*) 1fe7f397: ALSA: memalloc: Add vmalloc buffer allocation
                  support
    7e8edae3: ALSA: pcm: Handle special page mapping in the
                  default mmap handler

Link: https://lore.kernel.org/r/20191105151856.10785-12-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/6fire/pcm.c

@@ -449,13 +449,13 @@ static int usb6fire_pcm_close(struct snd_pcm_substream *alsa_sub)
 static int usb6fire_pcm_hw_params(struct snd_pcm_substream *alsa_sub,
 		struct snd_pcm_hw_params *hw_params)
 {
-	return snd_pcm_lib_alloc_vmalloc_buffer(alsa_sub,
+	return snd_pcm_lib_malloc_pages(alsa_sub,
 					params_buffer_bytes(hw_params));
 }
 
 static int usb6fire_pcm_hw_free(struct snd_pcm_substream *alsa_sub)
 {
-	return snd_pcm_lib_free_vmalloc_buffer(alsa_sub);
+	return snd_pcm_lib_free_pages(alsa_sub);
 }
 
 static int usb6fire_pcm_prepare(struct snd_pcm_substream *alsa_sub)
@@ -560,7 +560,6 @@ static const struct snd_pcm_ops pcm_ops = {
 	.prepare = usb6fire_pcm_prepare,
 	.trigger = usb6fire_pcm_trigger,
 	.pointer = usb6fire_pcm_pointer,
-	.page = snd_pcm_lib_get_vmalloc_page,
 };
 
 static void usb6fire_pcm_init_urb(struct pcm_urb *urb,
@@ -659,6 +658,8 @@ int usb6fire_pcm_init(struct sfire_chip *chip)
 	strcpy(pcm->name, "DMX 6Fire USB");
 	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &pcm_ops);
 	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &pcm_ops);
+	snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_VMALLOC,
+					      NULL, 0, 0);
 
 	rt->instance = pcm;